Lawn mowers are well known having a housing supported for movement over the ground by a plurality of wheels. A handle assembly extends upwardly and rearwardly from the housing to allow the operator to push and manipulate the housing. The housing includes a cutting chamber which encloses a cutting blade that rotates in a generally horizontal cutting plane. A lawn mower of the type just described is often known as a walk behind rotary lawn mower.
Many such rotary lawn mowers have housings that are integrally cast out of a metallic material, e.g. from steel or aluminum. Such housings are durable and strong, but relatively heavy and/or expensive to manufacture.
Other lawn mowers are known utilizing decks formed or molded from plastic. While such decks are lighter and may be less expensive depending upon the grade of plastic used, they often lack strength and durability. For example, rocks and other debris are sometimes picked up by the cutting blade and circulated within the cutting chamber. Decks molded from a plastic material are prone to being chipped or damaged by such rocks or similar debris.
Some rotary lawn mowers have a housing which may incorporate more than one material. For example, U.S. Pat. No. 4,189,903 to Jackson discloses a mower having a normal metallic deck. However, a mulching liner can be added to the deck to convert the mower to a mulching mower, the liner being molded from plastic. Thus, when the liner is in place, the mower comprises a metallic deck with a nested plastic liner.
The liner in the Jackson patent is for the purpose of converting the mower to a mulching mower as the liner includes various formed vanes or ribs for coacting with and deflecting the grass circulating within the liner. However, since the liner is made of plastic, it still exhibits various durability problems. Again, rocks or other debris might chip or damage the liner. Moreover, the liner does not add or contribute to the strength of the mower housing. That is provided by the fully formed metallic deck which is sufficiently strong by itself to form the mower housing if mulching is not desired. Thus, the basic strength of the housing is provided entirely by the metallic deck and not by the deck/liner combination, requiring the deck to be manufactured to the same strength standards as any normal mower metallic deck.